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Human Reproduction Test - 49

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Human Reproduction Test - 49
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  • Question 1
    1 / -0
    Spermatogenesis is induced by
    Solution
    At puberty, the hypothalamus begins to secrete gonadotropin-releasing hormone (GnRH). GnRH stimulates the anterior pituitary to secrete the gonadotropic hormones follicle-stimulating hormone (FSH) and luteinizing hormone (LH). 
    Both FSH and LH are glycoproteins, that use cyclic AMP as a second messenger. FSH stimulates Sertoli cells to secrete androgen-binding protein (ABP) and other signaling molecules, that are necessary for spermatogenesis. 
    LH stimulates the interstitial cells to secrete testosterone. FSH, LH, and testosterone all directly or indirectly stimulate testosterone secretion and spermatogenesis. 
    A high concentration of testosterone in the testes is required for spermatogenesis. Testosterone and FSH stimulate Sertoli cells to produce ABP, which binds to testosterone and concentrates it in the tubules. Testosterone also maintains the male secondary sex characteristics.
    Therefore, the correct answer is option A.
  • Question 2
    1 / -0
    Double axial gradient theory was given by
    Solution
    Original gradient theory was given by T. Boveri and was supported by M. C. Child. Child called it as a metabolic axial gradient theory. According to it, the egg has distinct animal and vegetal poles. The cytoplasm of the animal pole divides rapidly but the rate of cleavage in the vegetal pole is slow. It indicates that the rate of metabolism is more in the animal pole than the vegetal pole which is called as a metabolic axial gradient. Horstadius and Runnstrom called it as double gradient theory. They explain egg development on the basis of animal pole gradient and vegetal pole gradient. Hence, the correct option is D.
  • Question 3
    1 / -0
    How many sperms are produced from first spermatocyte?
    Solution
    One primary spermatocyte (2n) undergoes meiosis I and produces two daughter cells, each of which is called a secondary spermatocyte. 
    A secondary spermatocyte (n) then undergoes meiosis II and produces two daughter cells called spermatids (n). 
    These spermatids undergo spermiogenesis to each become sperm (n). Therefore 4 sperms are produced from the first spermatocyte. Hence option A is correct.
  • Question 4
    1 / -0
    Meroblastic cleavage is
    Solution
    The telolecithal eggs of reptiles and birds have very large amounts of yolk at the vegetal pole and only a small amount of cytoplasm concentrated at the animal pole. The yolk of such eggs never cleaves. Cell division is restricted to the blastodisc, the small disc of cytoplasm at the animal pole; this type of cleavage is termed meroblastic cleavage. 
    In the presence of a large amount of yolk in the fertilized egg cell, the cell can undergo partial, or meroblastic, cleavage.
  • Question 5
    1 / -0
    Which of the following controls the function of Sertoli cells?
    Solution
    Each testicular lobule contains one to three highly coiled seminiferous tubules in which sperms are produced. Each seminiferous tubule is lined on its inside by two types of cells, called as male germ cells (spermatogonia) and Sertoli cells. 
    The male germ cells undergo meiotic divisions finally leading to sperm formation, while Sertoli cells provide nutrition to the germ cells. Spermatogenesis starts at the age of puberty due to significant increase in the secretion of gonadotropin releasing hormone (GnRH). This is a hypothalamic hormone. The increased levels of GnRH then acts at the anterior pituitary gland and stimulates secretion of two gonadotropins luteinising hormone (LH) and follicle stimulating hormone (FSH). LH acts at the Leydig cells and stimulates synthesis and secretion of androgens. Androgens, in turn, stimulate the process of spermatogenesis. FSH acts on the Sertoli cells and stimulates secretion of some factors, which help in the process of spermiogenesis.
  • Question 6
    1 / -0
    Cleavage found in mesolecithal egg is
    Solution
    In the absence of a large concentration of yolk, four major cleavage types can be observed in isolecithal cells (cells with a small even distribution of yolk) or in mesolecithal cells (moderate amount of yolk in a gradient) - bilateral holoblastic, radial holoblastic, rotational holoblastic and spiral holoblastic cleavage.
  • Question 7
    1 / -0
    The function of vas deferens is to
    Solution
    The vas deferens is a long, muscular accessory gland that conducts mature sperm from the epididymis to urethra. This tube travels from the epididymis into the pelvic cavity, to just behind the bladder. Thus, the correct answer is option B.
  • Question 8
    1 / -0
    Which of the following statements is correct?
    Solution
    During luteal phase of the ovarian cycle, the ovulated Graafian follicle is differentiated into corpus luteum under influence of LH. It secretes estrogens and progesterone. In absence of implantation, progesterone and estrogens exert negative feedback control over the anterior pituitary’s secretion of LH and cause degeneration of corpus luteum in the ovary within 10 days of its formation. 
    The degenerated corpus luteum is present as white scar known as corpus albicans. This makes option A correct. The lower progesterone level, as caused by the disintegration of corpus luteum, results in disintegration of endometrium thereby initiating the next menstrual cycle. If fertilization is followed by implantation, the placental hormone human chorionic gonadotropin maintains the corpus luteum. This makes option B incorrect. 
    Corpus luteum continues to secrete progesterone to maintain the uterine endometrium and inhibit menses for about 6 months till placenta starts secretion of progesterone and estrogens. Once placenta starts secretion of progesterone, corpus luteum degenerates into corpus albicans. This makes option C incorrect. 
    Lower levels of progesterone can cause abortion/miscarriage due to the disintegration of the endometrium, which means that corpus luteum is necessary to maintain pregnancy; option D is incorrect. The correct answer is A.  
  • Question 9
    1 / -0
    The nutritive cells found in seminiferous tubules are
    Solution
    The large sustentacular cells that extend from the capsule to the lumen of the seminiferous tubule are called Sertoli cells. They serve to support, nourish, and regulate the maturation of sperm cells during spermatogenesis. 
    So, the correct answer is option A.

  • Question 10
    1 / -0
    After ovulation, endocrine part of ovary is
    Solution
    • Corpus luteum is a glandular structure developed from the ruptured graafian follicle after the release of ovum i.e. ovulation.
    • Before ovulation, there internal cells of ovarian follicles are major source of endocrine hormones.
    • After ovulation, corpus luteum acts as a temporary endocrine gland. It secretes large quantity of progesterone and small amount of estrogen.
    • So, the correct option is 'Corpus luteum'.
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